On the Information-Detecting Capacity of Photographic Emulsions*

The concepts of quantum efficiency and detecting capacity of photographic emulsions are discussed with reference to the granularity, spread function, and characteristic curve of the emulsion. A measure of informational sensitivity is introduced which depends on these quantities and provides an objective measure of performance of emulsions when they are compared at their optimum working scales. In terms of this measure, as well as from a direct visual appraisal of picture quality, it appears that two emulsions, such as Kodak Tri-X Film and Kodak Panatomic-X Film, can have widely different sensitometric speeds but quite similar informational sensitivities.